How do you change heater core on 2001 ZX2?

If you have not done this before, it is a very time consuming job. Replacing the heater core is not the problem. Getting to it is. Unless you are willing to start removing panels and know how to remove them without damaging the plastic panels and clips, I suggest you take it to a professional. It is just a matter of removing enough to actually get to the core. Once you get to the heater core, first drain the radiator enough to get the level below the heater hoses. Remove the heater hoses, and then remove and replace the core.